The invention generally relates to systems and methods for displaying traffic information on a display unit. In particular, the disclosed embodiments relate to systems and methods for displaying air traffic on a traffic display unit, such as a navigation display located in the cockpit or flight deck of an aircraft.
The term “traffic display unit” will be used hereinafter to refer to display units that display symbols representing vehicular traffic of interest to a display unit viewer. Thus the term “traffic display unit”, as used herein, includes navigation displays and other types of traffic display units onboard aircraft.
Modern aircraft typically include cockpit displays that are controlled by an information system. Cockpit displays include the basic displays that are supplied with the aircraft, and other add-on displays which vary in their degree of integration with the physical aircraft structure and aircraft systems. In a modern electronic cockpit, the flight instruments typically include a so-called “navigation display”. A navigation display (which may be adjacent to the primary flight display) along with navigational information may show the current position of all aircraft within the display range and information. Current implementations of a navigation display range selection are typically in whole number increments (for example, 640, 320, 160, 80, 40, 20, and 10 nautical mile ranges) such that intermediate display range selections between the whole number increments are not utilized.
Many modern aircraft are equipped with a traffic collision avoidance system (TCAS) that monitors surrounding airspace for similarly TCAS-equipped aircraft, independent of air traffic control, and issues an alert when a conflict (i.e., a potential collision threat) with another aircraft is identified. (The term “conflict” as used herein is an event in which two aircraft experience a loss of minimum separation. A conflict occurs when the distance between aircraft in flight violates a defining criterion, usually a minimum horizontal and/or minimum vertical separation. These distances define an aircraft's protected zone, a volume of airspace surrounding the aircraft which should not be infringed upon by any other aircraft.) Each TCAS-equipped aircraft interrogates all other aircraft in a specified range, and all other aircraft reply to the interrogations which they receive. The TCAS comprises a processor, a directional antenna mounted on the top of the aircraft, an omnidirectional or directional antenna mounted on the bottom of the aircraft, and a traffic display in the cockpit. The TCAS traffic display may be integrated into the navigation display or some other cockpit display. The TCAS processor builds a three-dimensional map of aircraft in the airspace, incorporating their range, closure rate, altitude and bearing; then the TCAS processor determines if a conflict exists by extrapolating current range and altitude difference to anticipated future values and determining whether another aircraft has entered a protected volume of airspace that surrounds ownship. The extent of the protected volume of airspace will depend on the altitude, groundspeed and heading/track of the aircraft involved in the encounter.
More specifically, the TCAS processor executes a program that performs a conflict detection algorithm. Based on parameters applied by the conflict detection algorithm, the TCAS gives an alert when several conditions occur: (1) Entry by an intruder into a protected airspace (called the Traffic Advisory region) surrounding the ownship causes the TCAS onboard that aircraft to issue a Traffic Advisory (hereinafter “TA”). (2) If the opposing traffic is within the protected airspace and the TCAS detects that the heading/track, climb rate, and closure rate of the opposing traffic may cause it to collide with the ownship; the TCAS issues a Resolution Advisory (hereinafter “RA”).
In addition, a significant number of aircraft flying today are also equipped with the Automatic Dependent Surveillance-Broadcast (ADS-B) system and by year 2020 all aircraft operating within the airspace of the United States must be equipped with some form of ADS-B. The ADS-B system enhances safety by making an aircraft visible in real-time to air traffic control and to other suitably equipped aircraft. The ADS-B technology enhances safety by enabling display of traffic positions and other data, in real-time, to Air Traffic Control (ATC) and to other appropriately equipped ADS-B aircraft, with position (i.e., latitude, longitude and altitude), velocity (i.e., groundspeed) and other data being transmitted every second. Using this information, a traffic processor onboard a receiving aircraft can calculate the current heading/track and a future position of a transmitting aircraft. When using an ADS-B system, a pilot is able to receive traffic information about aircraft in his vicinity and at farther distances. The ADS-B system relies on two avionics components—a high-integrity GPS navigation source and a data link (ADS-B unit) connected to other aircraft systems. ADS-B enables cockpit display of traffic information for surrounding aircraft, including the identification, position, altitude, heading/track and groundspeed of those aircraft. With the use of ADS-B traffic, the flight crew is given more information about traffic heading/track, groundspeed and position. Using that information, the flight crew must perform monitoring tasks to keep track of traffic in their vicinity and then estimate whether traffic may cross their path in the future or cause a TA/RA conflict in the future.
In today's airspace, air traffic controllers instruct the flight crew to maintain visual separation from the aircraft in front (referred to herein as “the leading aircraft”) for approach and landing. In such clearances, the flight crew is responsible for maintaining separation from the aircraft in front. If the flight crew loses visual contact with the leading aircraft due to small patches of clouds or the background lights at night time, the flight crew is expected to execute a missed approach, resulting in extra fuel cost and time.
Accordingly, there is a need for electronic traffic display units that operate in accordance with associated alerting algorithms to enable the flight crew to continue the approach and land the aircraft even if they lose visual contact with the a leading aircraft.